One of the first questions on any extension project is whether you need planning permission. The good news is that many single-storey extensions can be built under permitted development rights without a full application. The rules are detailed, so this is a summary rather than legal advice, and we always recommend confirming with your local planning authority.
Permitted development, in brief
- Single-storey rear extensions can extend up to 4 metres from the original rear wall on a detached house, or 3 metres on a semi or terrace. Larger extensions up to 8 and 6 metres are possible through the prior approval process.
- The extension must not be higher than 4 metres, and the materials should be similar in appearance to the existing house.
- Side extensions must be single storey, no wider than half the width of the original house.
- Two-storey extensions are more restricted and must be at least 7 metres from the rear boundary.
When you will need an application
Listed buildings, conservation areas, flats, and houses where permitted development rights have been removed all need a full application. So does anything that goes beyond the limits above, or a design with a balcony, raised platform or unusual roof.
Building regulations are separate
Even when planning permission is not needed, building regulations approval always is. This covers the structure, insulation, drainage, fire safety and electrics. We work with building control on every extension so the sign-off is in place at the end.
How we can help
Send us your ideas and we will tell you, from experience, which route your project is likely to need and introduce you to architects we trust if drawings are required.
